Polymerases are enzymes that catalyze the formation of polymers from monomers. Thus, DNA polymerases are enzymes that synthesize deoxyribonucleic acid (DNA) from deoxynucleotide triphosphates. DNA dependent DNA polymerases are enzymes that use DNA as a template to synthesize DNA, and as such are critical to biological processes, including DNA replication.
DNA polymerases also find use in a variety of microbiological applications, such as sequencing, in vitro polynucleotide synthesis, and the like. With the advent of the polymerase chain reaction and the multitude of applications based thereon, the use of DNA polymerases has increased dramatically.
Of particular interest to the academic and industrial communities are thermostable polymerases capable of retaining their polymerase activity through the significant temperature modulations that characterize the polymerase chain reaction. A variety of different naturally occurring thermostable polymerases have been isolated and characterized to date. Typically such thermostable polymerases are isolated from prokaryotic hosts which live in climates characterized by high temperature, e.g. natural hot springs, volcanic vents and the like. Representative naturally occurring thermostable polymerases include: Thermus aquaticus DNA polymerase; Thermus thermophilus DNA polymerase; Thermococcus litoralis DNA polymerase; Thermotoga maritima DNA polymerase; Pyrococcus furiosus DNA polymerase; and the like.
In addition to their polymerase activity, naturally occurring DNA polymerases from bacterial hosts typically also exhibit 5'-exonuclease activity. For many academic and industrial applications, this exonuclease activity is undesirable. As such, a number of synthetic polymerases, e.g. truncation or deletion mutants of naturally occurring polymerases, have been developed which exhibit reduced exonuclease activity as compared to their naturally occurring counterparts.
In view of the ever increasing use of the polymerase chain reaction in today's academic and industrial communities, there continues to be interest in the identification of new thermostable enzymes that exhibit polymerase activity.